This invention relates to monitoring and controlling the pressure of fluid in the eye during eye surgery.
The anterior region of the eye is a small, fluid-filled chamber. During surgery, fluid balance in the eye is maintained by supplying irrigation fluid to the eye and aspirating fluid from the eye using a surgical instrument. One such instrument, particularly useful in removing cataracts, is a phaco-emulsification instrument, which includes an ultrasonically vibrated hypodermic needle inserted into an incision in the eye to break up the cataract lens. The lens fragments and aspirated fluid are removed by suction through the needle. Typically, the surgical instrument is connected to the source of irrigation fluid and a drainage bag with a tube set that includes a series of individual, interconnected irrigation and aspiration tubes. After the procedure has been completed, the tube set is disassembled, and is either sterilized and reused or replaced with a new set of tubes for the next procedure.
To avoid damaging the eye, the rate at which irrigating fluid is supplied to the eye and aspirated (generally by inducing a vacuum in the aspiration tube using, e.g., a peristaltic pump) is controlled to ensure that the intraocular pressure remains within acceptable limits. Typically, such control is achieved by monitoring the vacuum in the aspiration tube with an electronic sensor connected to a branch of the aspiration tube. The rate at which fluid is supplied to the eye and/or aspirated from the eye is controlled based on the vacuum in the branch as measured by the sensor.